Allowable solar flux densities for molten-salt receivers: Input to the aiming strategy

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Solar Power Tower technology requires accurate models and tools to assist in design and operation stages. The heliostat field aiming strategy seeks the maximization of the thermal output from the receiver, while preventing its permanent damage because of thermal stress and corrosion in molten salt receivers. These two limitations are translated into Allowable Flux Densities (AFD), which can be handled by the aiming strategy. This paper explains the methodology to determine AFDs, and analyzes the influence of tube geometry and material. AFD by corrosion is slightly lower in Haynes 230 than Inconel 625 and austenitic alloys. On the contrary, HA230 has better performance than In625 under thermal stress. Increment of tube wall thickness diminishes the AFD: slightly by corrosion, but significantly by thermal stress. The generated AFD databases feed the aiming model, herein applied to Gemasolar case study. In the cylindrical receiver, first northern panels are limited by thermal stress, while the last ones by corrosion. Under optimized aiming, HA230 receiver tubes produce equivalent thermal output than In625. • Corrosion AFD increases with mass flow rate, but decreases with salt temperature. • Stress AFD increases with salt temperature, but decreases with wall temperature. • Tube thickness has dramatic effect on thermal stress, while not on corrosion. • Receiver first panels restricted by thermal stress, while last ones by corrosion. • HA230 better mechanical performance is traded off by In625 higher corrosion tolerance.